The present invention relates to semiconductor fabrication and, more particularly, to methods and systems for collecting divergent chemistries in a wafer cleaning chamber.
In the fabrication of semiconductor devices, wafers are cleaned in wafer cleaning chambers, such as spin, rinse and dry modules. For a single wafer cleaning operation, it is well known to those skilled in the art, that various cleaning chemistries are applied to a wafer in order to clean the wafer following a previous processing operation. FIG. 1 is a simplified schematic diagram of a conventional single-wafer cleaning chamber also known as a spin, rinse and dry module. As shown in FIG. 1, wafer 104 is supported in a cleaning chamber 102. Wafer 104 is rotating around axis 110 in direction 106. While wafer 104 is rotating, fluid (i.e., cleaning chemistry) is applied to the top surface of the wafer. As the fluid is spun-off of the top surface of wafer 104, the walls and the bottom portions of cleaning chamber 102 become coated with the fluid due to spray-off during wafer rotation.
The fluid falling to the floor of cleaning chamber 102 is collected through drain 112. Once a first fluid has been applied to wafer 104, the cleaning chamber 102 is rinsed in preparation for application of a second fluid. Each fluid and subsequent rinsing agent is received by drain 112 and then either sent to a location to be disposed of or to be recycled. Since a single drain 112 collects the effluent, separation and collection of the chemical waste streams becomes difficult.
Another shortcoming of the system described with reference to FIG. 1, is that the cleaning chemistry is spread over a large inner surface area of the cleaning chamber. Thus, some of the fluid may not be successfully reclaimed. That is, where a first cleaning chemistry is followed by a second cleaning chemistry, the second cleaning chemistry may not be able to be recycled. The lack of ability to recycle the second cleaning chemistry may be due to the excessive time to obtain a pure chemical stream that is not diluted by the remaining residues of the first cleaning chemistry or any rinsing agent. This loss can be problematic when expensive cleaning chemistries are used. Additionally, the rinsing of the cleaning chamber between different cleaning chemistry applications requires extra processing time, in addition to a large amount of rinsing agent, to thoroughly remove any of the previous cleaning chemistry from the inside surface of the cleaning chamber. Therefore, rinsing the chemical effluent remaining in the cleaning chamber adds to the time and cost of wafer cleaning operations. Consequently, current cleaning chamber designs are inadequate to capture effluent efficiently for recycling or waste treatment.
In view of the foregoing, there is a need for a process to increase the efficiency of chemistry collection and rinsing in wafer cleaning chambers.